In wooden construction, a construction metal piece previously formed with a number of nail holes is frequently used in connecting a column member, a beam member and a girder member or the like, or for reinforcing connecting portions of the structure members. The construction metal pieces are struck to fasten to a structure member of a column or the like by nails. In striking to fasten such a construction metal piece previously formed the nail hole, a nailing machine made to continuously strike a nail by power of compressed air or the like is used. According to the nailing machine made to strike the nail into the nail hole of the construction metal piece, the nail is struck into the nail hole by starting the nailing machine in a state of arranging the nail supplied into the injection port for slidably guiding the driver driven by power such that a tip of the nail is projected from a front end of the injection port and inserting the tip of the nail projected from the front end of the injection port into the hole of the construction metal piece.
In one mechanism for projecting the tip portion of the nail from the front end of the injection port before starting the nailing machine, connected nails connected in a skewed direction by making nail axes in parallel with each other and shifting the respective nails in an axial direction are charged into a magazine continuously provided to the nose portion forming the injection port, a tip of a front one nail supplied from the magazine into the injection port of the nose portion is projected from the front end of the injection port, the tip of the nail is inserted into the hole of the meal piece and the nail is struck by positioning the nailing machine. Further, in other mechanism, a push piston mechanism sliding along the injection port of the nose portion is provided, prior to striking the nail by the driver, the push piston mechanism cut to separate the front one of the connected nails supplied into the injection port from a connected state to press to a direction of the front end of the injection port and the tip portion of the nail is held to be projected from the front end of the injection port.
However, in the former mechanism, the front nail of the connected nails connected by way of a connecting band is projected from the injection port and the tip of the nail is inserted into the hole of the construction metal piece to thereby position the nail machine and therefore, there poses a problem that the front nail is supported by a rigidity of the connecting band of the connected nails and operation of positioning the nail machine becomes unstable. Further, according to the latter mechanism, the push piston mechanism for moving the nail supplied into the injection port to the direction of the front end of the injection port needs to be installed to the nose portion, cost is increased, further, an outer shape of the nose portion becomes large to hamper operability.
Further, according to the mechanisms, the nailing machine is guided to the nail hole of the construction metal piece by the tip of the nail projected from the injection port of the nose portion and therefore, a safety mechanism for starting the nailing machine by pressing a contact member arranged to be projected frontward from the nose portion to the struck member and by a trigger operated by the hand grabbing a grip cannot be used. Therefore, there poses a problem of needing a safety apparatus by a complicated mechanism of operating to project a contact member in the direction of the front end along the nose portion by operating the trigger after positioning the tip of the nail projected from the injection port at inside of the nail hole and starting the nailing machine when the contact member impinges on the struck member and cannot be moved to the position projected to the front end side of the nose portion.
In order to deal with the problems, according to the nailing machine disclosed in JP-A-08-052666, a nail guide member a shape of an outer peripheral face of a front end portion of which is constituted by a shape of cutting to halve a converging taper in a longitudinal direction is arranged on the front side of the detection port formed at the nose portion, and the nailing machine is positioned by inserting the front end portion of the guide member in the shape of the half cut converging taper into the nail hole of the construction metal piece. By guiding the tip of the nail struck out from the injection port along a guiding guide groove formed at a rear side face of the guide member, the nail is guided into the nail hole of the construction metal piece to be struck into the nail hole.
According to the nailing machine of JP-A-08-052666, as shown by FIG. 10, when the nail is struck by making the nail striking direction of the nail machine orthogonal to a face of a struck member, a front end portion 51 of a nail guide member 50 formed in the shape of the half cut taper is fitted to a position of substantially a half of inside of a nail hole H of a construction metal piece M. Therefore, the nail can firmly be struck into the nail hole H of the construction metal piece M by guiding the tip of the nail struck by being guided along a guiding guide groove 52 of the nail guide member 51 into the nail hole H. However, at a construction site, there is a case in which the nail striking direction of the nailing machine cannot necessarily be maintained to be orthogonal to the face of the struck member and there is a case in which the nailing machine is operated by being inclined to a front side. In this case, as shown by FIG. 11, when the nail guide member 50 is inclined to the front side, the front end portion 51 of the nail guide member 50 in the shape of the half cut taper is inclined by being slipped to a rear side at inside of the nail hole H of the construction metal piece M. The front end portion 51 of the guide member 50 impinges on an edge portion on the rear side to close the nail hole H and an axial line direction of the nail N guided by the guiding guide groove 52 is not guided into the nail hole H of the construction metal piece M.
When the nail is struck by starting the nailing machine in the inclined state in this way, the tip of the nail guided by the nail guide member 50 impinges on the surface of the construction metal piece M, the nail jumps back in an unexpected direction and therefore, the operation is extremely dangerous. Further, although since the front end portion 51 of the nail guide member 50 is formed to be thin, the front end portion 51 is easy to be destructed and needs to be interchanged frequently, in interchanging the nail guide member 50, a tool of a spanner, a screwdriver or the like is needed to pose a problem that the nail guide member 50 cannot easily be interchanged at an operation site.